Facing sheet for an absorbent article and method for producing same

ABSTRACT

A facing sheet (10) for absorbent articles is disclosed in the form of a laminate made up of at least a first layer (12) and a second layer (14). The first layer is intended to face a wearer when the absorbent article is in use and presents a plurality of through holes (16) delimited by an upper perimeter (18) and a lower perimeter (20) to thereby permit liquid to migrate through to the second layer (14). The second layer presents first depressions (22) which are arranged such that the lower perimeter (20) of each hole in the first layer (12) is aligned with an associated depression in the second layer (14). The invention further relates to a method which may be used to produce such a facing sheet.

TECHNICAL FIELD

The present invention relates to a facing sheet for an absorbent articleaccording to the preamble of claim 1 and claim 7, and a method ofproducing a facing sheet according to the preamble of claim 8 and claim9.

BACKGROUND OF THE INVENTION

Absorbent articles such as sanitary napkins, disposable diapers andincontinence pads are generally made up of an absorbent core sandwichedbetween a liquid permeable facing sheet and a liquid impermeable backingsheet. The facing sheet contacts the wearer and is either naturallypermeable or is apertured to allow discharged bodily fluids to passthrough the facing sheet to be thereafter retained in the absorbentcore.

With absorbent articles of this nature, it is of particular importancethat the facing sheet imparts the impression of dryness, even when thearticle has been worn for an extended period of time. In addition, thefacing sheet must feel comfortable when contacting the skin of thewearer.

Whilst the facing sheet must be permeable to allow fluid to pass throughto the absorbent core, the facing sheet should not suffer from rewettingwhen the absorbent article is subjected to compressive forces which mayarise as a result of movement of the wearer. On the other hand, it isimportant that the apertures in the facing sheet remain open even whenthe absorbent article is compressed, otherwise discharged fluid willcollect on the surface of the facing sheet.

Various facing sheets are documented in patent literature. By way ofexample, an apertured plastics facing sheet is disclosed in U.S. Pat.No. 4,626,254 in which the apertures are located in depressions arrangedin the upper layer of the facing sheet, with the apertures being formedin vertical walls of the depressions. Such a facing sheet is howeverrelatively complicated to manufacture since high precision is requiredto form the apertures.

A facing sheet is described in EP-A-0 235 309 which comprises non-wovenfabric having two layers of different fibre compositions. The layer ofthe fabric which faces the wearer is apertured. Such a facing sheet ismade by forming the first layer by subjecting a fibrous web to a highvelocity water jet treatment on a support carrying aperture formationelements, forming the second layer by subjecting a fibrous web to eitherwater treatment or heat fusion treatment, and simultaneously combiningthe first layer with the second layer by either of these treatments. Adisadvantage with such a process is that the process is utilizable on arestricted number of different materials only.

GB-A-2 235 878 describes a facing sheet made up of an aperturedhydrophobic resin film and a liquid retentive structure body having ahydrophillic surface and a three-dimensional skeleton structure. Theskeleton structure comprises a plurality of randomly distributed poreswhich communicate with the apertures in the resin film to allegedlyallow the rapid introduction of a liquid into an absorbent. Theapertures in the resin film may be formed by blow moulding and generallyhave a diameter lying between 1 and 5 mm. Due to the random distributionof the pores in the skeleton structure, it is difficult to accuratelypredict the rate of liquid take up of such a facing sheet.

An absorbent article is disclosed in U.S. Pat. No. 4,908,026 having aperforated liquid pervious bodyside liner and a flow zone control layerunderlying the perforated region of the bodyside liner. During theperforating process, loose elements of the bodyside liner becomeentangled with hairy meltblown fibres of the flow zone control layer. Itis stated that the loose elements are believed to aid in the transfer ofliquid through the flow zone control layer.

U.S. Pat. No. 4,341,217 describes an absorbent article having aperforated outer wrap of liquid impermeable material provided with amultiplicity of protuberances projecting toward an absorbent core. Byselecting a particular combination of size and depth of theprotuberances, it is asserted that the outer wrap can be made tofunction both as a topsheet portion and as a backsheet portion.

EP-A-0 214 608 describes an apertured facing sheet comprising anon-woven web network of essentially unbroken thermoplastic fibres. Eachaperture is formed by a heated pin which penetrates the nonwoven fabricand separates the fibres thereof, with heat from the pin causing theseparated fibres to consolidate and set to prevent subsequent closing ofthe hole. A disadvantage with such a facing sheet is that the equipmentnecessary for its manufacture requires very close tolerances since eachpin tip has to pass into a corresponding hole with perfect clearance.Again, such apparatus is suitable only for making relatively largediameter apertures.

A further process for forming an apertured plastics facing sheet is toheat a plastic film with hot air as the film passes around an aperturedroll. By applying a vacuum within the roll, portions of the plastic filmare drawn into the apertures of the roll and burst to thereby createcorresponding apertures in the facing sheet. Due however to theapplication of heat, the properties of the sheet are altered. Inaddition, the lower periphery of each of the thus burst apertures isuneven and the apertures themselves have a tendency to close when thesheet is subjected in use to compressive forces.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a facingsheet having an apertured first layer which fulfils the requirements ofcomfort and cleanliness and which is easier to manufacture than previousfacing sheets.

This object is achieved by a facing sheet according to claim 1 and afacing sheet according to claim 7.

It is a further object of the present invention to provide a method ofproducing a facing sheet for use in an absorbent article in which thehole size and dispersion can be accurately controlled to provide exactflow characteristics of a liquid through the facing sheet.

This object is achieved in accordance with the present invention by amethod according to claim 8 and a method according to claim 9.

Preferred embodiments of the facing sheet and method are detailed in therespective dependent claims.

The provision of depressions in the second layer of the facing sheetaccording to the invention implies that the surface area of material ofthe second layer which is exposed to the liquid as it flows through theholes in the first layer can be selected depending on the depth of thedepressions. In addition, the greater the depth of depression, theshorter the flow path through the second layer to the underlyingabsorbent core. In this manner, the flow characteristics of the liquidthrough the facing sheet to the underlying absorbent core can beaccurately controlled. That material of the facing sheet is removed by amilling process implies that very accurate control of the depth ofmaterial removal can be attained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in the following in greater detail byway of example only and with reference to the attached drawings, inwhich

FIG. 1 is a schematic perspective view of a portion of facing sheetaccording to the invention;

FIG. 2 is a schematic sectional view along line II--II of FIG. 1, thoughon a larger scale;

FIGS. 3 and 4 correspond to FIG. 2, though illustrate differentembodiments of the facing sheet according to the invention;

FIG. 5 is a schematic representation of one stage in the manufacturingprocess for making a facing sheet, whilst

FIG. 6 shows on an enlarged scale a portion of the equipment illustratedin FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the drawings, reference numeral 10 generally denotes a facing sheetaccording to the present invention. The facing sheet is intended to beused in absorbent articles such as sanitary towels, diapers or bandageswhich, in addition to a facing sheet, further comprise a liquidimpermeable backing sheet and an absorbent core located therebetween.

The facing sheet 10 illustrated in FIGS. 1 and 2 comprises a laminatemade up of a first layer 12 and a second layer 14. Preferably, thelayers making up the laminate are substantially coextensive to therebyform a unitary, substantially homogeneous facing sheet. When used inconjunction with an absorbent article, the first layer 12 is uppermost,i.e. the first layer 12 is intended to face the wearer of the absorbentarticle. As is common in the art, the first layer is provided with aplurality of through holes 16. As is most clearly shown in FIG. 2, eachhole 16 is delimited by an upper perimeter 18 and a lower perimeter 20.In this manner, liquid discharged onto the first layer 12 can migratethrough the holes 16 to the second layer 14. Preferably, the first layer12 has a thickness between 5 and 30 μm and the second layer has athickness between 10 and 70 μm.

In accordance with one aspect of the present invention, the second layer14 presents first depressions 22 which are arranged such that the lowerperimeter 20 of each hole 16 in the first layer 12 is aligned with anassociated depression 22 in the second layer 14. By selecting a suitablesize of through hole 16 and depth of depression 22, the rate of flow ofdischarged liquid through the facing sheet 10 can be accuratelycontrolled. By way of example, a through hole 16 may have across-sectional area of between 1.0 and 25 mm², whilst a suitable depthfor a depression 22 may lie between 5 and 50 μm.

In order to hinder discharged bodily fluids from remaining on thesurface of the facing sheet 10, the first layer may comprise a generallyhydrophobic material and the second layer advantageously comprises agenerally hydrophillic material. As will be apparent from the subsequentdescription of the method in accordance with the invention for producinga facing sheet, since the method can be practised on a wide variety ofmaterials, the facing sheet of the present invention may include a firstlayer of film, nonwoven or woven fibres. Suitable materials includepolyethylene, polypropylene, polyester, acrylic, nylon, PVC, hydrophobiccotton fibres or similar. Typically, the first layer consists of apolyethylene-polypropylene film. The second layer may include any ofthese materials or rayon fibres, a foam-plastic, polyester or cellulosefibres.

A second embodiment of the facing sheet in accordance with the presentinvention is illustrated in FIG. 3. In common with the facing sheet ofFIGS. 1 and 2, the facing sheet in FIG. 3 comprises a first layer 12with through holes 16 and a second layer 14 with first depressions 22aligned with the through holes in the manner as described above. Incontrast to the previously described facing sheet, the facing sheet ofFIG. 3 is provided with a third layer 24 located between the first andsecond layer. This third layer advantageously comprises a plastics filmwhich serves to inhibit rewetting of the first layer. In order to permitliquid to migrate from the first layer 12 to the second layer 14, thethird layer 24 exhibits through holes 26 aligned with the through holes16 of the first layer.

A further embodiment of the facing sheet in accordance with the presentinvention is illustrated in FIG. 4. In this embodiment, the second layer14 presents second depressions 28 extending into the second layer to apredetermined depth measured from the surface of the second layer remotefrom the first layer. Advantageously, these second depressions lieoffset relative to the first depressions 22. In this manner, the lengthof the liquid flow path, i.e. the amount of material in the second layerthrough which discharged liquid must flow before reaching the underlyingabsorbent core, can be shortened whilst still maintaining adequatestrength in the facing sheet.

The above described embodiments of the facing sheet according to thepresent invention may advantageously be produced using the methoddescribed below which forms another aspect of the present invention.

Thus, the present invention provides a method for producing a facingsheet for absorbent articles in which the sheet has a first majorsurface and a second major surface and comprises at least two materiallayers. With particular reference to FIGS. 5 and 6, the method involvespassing the facing sheet 10 between a first set of rollers 30 comprisinga pattern roller 32 having a plurality of projections 34 and a millingcutter 36 having cutting edges 38 so that a portion of the materiallayer is removed to a predetermined depth from the first major surface.

As is most clearly apparent from FIG. 6, the projections 34 on thepattern roller 32 cause the facing sheet to be lifted in a region inwhich it is desired to remove material. Depending on the ratio betweenthe thickness of the facing sheet and the clearance between the uppersurface of the projection 34 and the cutting edge 38, a predetermineddepth of material can be removed from the facing sheet. The crosssectional area of each hole which is so produced is dependent on thecross sectional area of the projection 34, assuming that the cuttingedge 38 extends across the entire width of the projection.

It will be readily apparent that by providing pattern rollers havingdifferent sizes and distribution of projections, apertured facing sheetscan be produced having through holes of particular size and selectedposition.

Although the above method may be utilized on a facing sheet consistingof just one material layer, the method is eminently suitable forproducing the facing sheet as illustrated in FIGS. 1 to 4 in which aplurality of material layers is present.

Thus, and with reference to FIG. 2, when the facing sheet comprises alaminate made up of a first layer 12 having a first thickness t₁ and asecond layer 14 having a second thickness t₂, the predetermined depth ofthe material removed from the facing sheet is selected to be greaterthan the first thickness t₁ though less than the sum of the first andsecond thickness.

Similarly, and with reference to FIG. 3, when the facing sheet includesa third layer 24 having a third thickness t₃ located between the firstand second layer, the predetermined depth of material removed from thefacing sheet is chosen to exceed the sum of the first and thirdthickness, though is less than the sum of the first, second and thirdthickness.

The embodiment of the invention illustrated in FIG. 4 may be obtained byfirstly creating holes and depressions to a predetermined depth from thefirst major surface of the facing sheet as described above, and thensubsequently passing the facing sheet through a second set of rollerscomprising a pattern roller having a plurality of projections and amilling cutter having cutting edges so that a portion of said materiallayer is removed to a predetermined depth from the second major surface.

Naturally, it is to be understood that the present invention is notrestricted to the embodiments described above and shown in the drawings,but may instead be varied within the scope of the appended claims. Forexample, the number of material layers making up the facing sheet may bemore than three.

I claim:
 1. A facing sheet for absorbent articles comprising a laminatemade up of at least a first layer and a second layer, said first andsecond layers being substantially coextensive, said first layer beingintended to face a wearer when the absorbent article is in use andcomprising a plurality of through holes delimited by an upper perimeterand a lower perimeter to thereby permit liquid to migrate through to thesecond layer, said second layer presents first depressions which arearranged such that the lower perimeter of each hole in the first layeris axially aligned with an associated depression in the second layer,with each hole and associated depression being concentric, and saidsecond layer presents second depressions extending into said secondlayer to a predetermined depth measured from the surface of the secondlayer remote from said first layer.
 2. The facing sheet according toclaim 1, wherein said first layer comprises a generally hydrophobicmaterial and in that said second layer comprises a generallyhydrophillic material.
 3. The facing sheet according to claim 1, a thirdlayer is located between said first and second layer, said third layercomprising an apertured plastics film, the apertures of which areconcentric with the through holes of said first layer.
 4. The facingsheet according to claim 1, wherein said second depressions lie offsetrelative to said first depressions.
 5. The facing sheet according toclaim 1, wherein said first layer has a thickness between 5 and 30 μmand in that said second layer has a thickness between 10 and 70 μm.
 6. Afacing sheet for absorbent articles comprising a laminate made up of atleast a first layer and a second layer, said first and second layersbeing substantially coextensive, said first layer being intended to facea wearer when the absorbent article is in use and comprising a pluralityof through holes delimited by an upper perimeter and a lower perimeterto thereby permit liquid to migrate through to the second layer, saidsecond layer presents first depressions formed by the removal ofmaterial from said second layer, which depressions are arranged suchthat the lower perimeter of each hole in the first layer is axiallyaligned with an associated depression in the second layer, and saidsecond layer presents second depressions extending into said secondlayer to a predetermined depth measured from the surface of the secondlayer remote from said first layer.
 7. A method for producing a facingsheet for absorbent articles, said sheet comprising a laminate made upof a first layer having a first thickness and a second layer having asecond thickness, said first layer forming a first major surface of saidsheet and said second layer forming a second major surface of saidsheet, the method comprising the steps of passing the facing sheetbetween a first set of rollers comprising a pattern roller having aplurality of projections and a milling cutter having cutting edges sothat a portion of said material layer is removed to a predetermineddepth from said first major surface, said predetermined depth beinggreater than said first thickness though less than the sum of said firstand said second thicknesses.
 8. A method for producing a facing sheetfor absorbent articles, said sheet comprising a laminate made up of afirst layer having a first thickness, a second layer having a secondthickness and a third layer having a third thickness, wherein said thirdlayer is located between said first and second layer, said first layerforming a first major surface of said sheet and said second layerforming a second major surface of said sheet, the method comprising thesteps of passing the facing sheet between a first set of rollerscomprising a pattern roller having a plurality of projections and amilling cutter having cutting edges so that a portion of said materiallayer is removed to a predetermined depth from said first major surface,said predetermined depth exceeding the sum of said first and thirdthickness, though being less than the sum of the first, second and thirdthicknesses.
 9. The method according to claim 7, further comprisingsubsequently passing said facing sheet through a second set of rollerscomprising a pattern roller having a plurality of projections and amilling cutter having cutting edges so that a portion of said materiallayer is removed to a predetermined depth from said second majorsurface.
 10. The method according to claim 8, further comprisingsubsequently passing said facing sheet through a second set of rollerscomprising a pattern roller having a plurality of projections and amilling cutter having cutting edges so that a portion of said materiallayer is removed to a predetermined depth from said second majorsurface.
 11. The method according to claim 7, wherein the milling cutterremoves material from the first and second layers.
 12. The methodaccording to claim 8, wherein the milling cutter removes material fromthe first and second layers.